1. Field of the Invention
Aspects of the present invention relates to a polymer electrolyte. More particularly, aspects of the present invention relate to a polymer electrolyte having excellent ionic conductivity at high temperatures and that does not cause deformation of an electrolyte membrane, a method of preparing the same, and a fuel cell using the polymer electrolyte.
2. Description of the Related Art
Conventionally, ionic conductors, which are materials in which ions, such as, for example, protons, move when a voltage is applied, are widely known. Ionic conductors are used in electrochemical devices such as batteries, electrochemical sensors, or the like.
Fuel cells contain an ionic conductor, and, in terms of energy generating efficiency, system efficiency, long-term durability of constituent members, require a proton conductor that stably exhibits excellent proton conductivity for a long time at an operating temperature of 100 to 300° C. under non-humidified conditions or low-humidified conditions, such as a relative humidity of 50% or less.
Solid polymer-type fuel cells that meet this requirement have been developed. However, a solid polymer-type fuel cell that includes a perfluorocarbonsulfonic membrane as an electrolyte membrane has a disadvantage of insufficient energy generating efficiency at an operating temperature in the range of 100 to 300° C. under a relative humidity of 50% or less.
Further, there are fuel cells that include an electrolyte membrane having a substance that triggers proton conductivity, fuel cells that use a silica diffusion membrane, fuel cells that use an inorganic-organic composite membrane, fuel cells that use a phosphoric acid-doped graft membrane, and fuel cells that use an ionic liquid composite membrane.
In addition, a solid polymer electrolyte membrane formed of polybenzimidazole doped with a strong acid, such as a phosphoric acid or the like, is disclosed in U.S. Pat. No. 5,525,436.
However, such solid polymer electrolyte membranes described above cannot stably exhibit energy generating efficiency for a long time at high temperatures. In particular, long term stability is insufficient at a high operation temperature of 100 to 300° C. under non-humidified conditions or in a relative humidity of 50% or less.